<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>任务1</title>
    <style type="text/css">
        .p2 { background-color: #00539F;
            font-size: 2em;
            text-align: center; }
    </style>
    <link rel="stylesheet" href="style1.css">
</head>
<body>
<p style="background-color: #00539F;font-size: 2em;text-align: center;">
    Hello World内联
</p>
<p class="p2">
    Hello World2嵌入
</p>
<p id="p3">
    Hello World3外链
</p>
</body>
</html>